ROHM Delivers Dramatically Higher Output and Precision in the Industry's First LED Driver LSI for Automotive Tail Lamps！

2011-04-07

Kyoto, Japan – Semiconductor manufacturer ROHM CO., LTD., has developed the BD8372HFP-M driver LSI specifically for use with automotive LED tail lamps, a market that continues to experience a high rate of growth. In addition to delivering 200 mA of output to markedly exceed the 120 mA considered necessary for powering these lights, the new driver LSI offers dramatically higher output current precision of ±3%. This parameter, which affects LED brightness, is less than half the value obtainable from previous LSI designs, and the new LSI exhibits just one-fourth the variation of chips consisting of discrete components. ROHM began shipping samples of the new product in March (sample pricing: ¥300/part) and plans to begin mass production with an initial monthly volume of 50,000 parts in June 2011. The company plans to split production into a pre-process handled by ROHM Wako Co., Ltd., (Okayama Prefecture) and a post-process handled by ROHM Integrated Systems (Thailand) Co., Ltd., (Thailand).

Automakers have been rushing to switch to LED lighting for automotive tail lamps in a trend that is expected to continue against the backdrop of the lower power consumption and longer service life promised by the technology. Current LED tail lamps consist of 10 to 20 LED devices, but demand for designs with fewer LED devices and other components is increasing as high-brightness LEDs become available and the technology enters into widespread use in popular models. In light of these market trends and heightened demand for higher-precision, higher-output designs, the time was ripe for the development of a high-performance automotive tail lamp LED driver. The new ROHM tail lamp LED driver paves the way for higher-brightness LEDs by providing 200 mA of output current, about three to five times what is possible with previous LED drivers. At the same time, the dramatic improvement in output current precision offered by the product will make a major contribution to improved yields in tail lamp assembly processes by broadening the tolerances for LED variation. Furthermore, the new part's reliance on a source driver design that uses just one wiring connection between the driver IC board and LED board, compared to two connections in conventional sink driver designs, makes it easier to implement the open/short detection functionality required in automotive applications. The BD8372HFP-M promises unparalleled convenience for designers of automotive tail lamps, for example through independent current settings so that brightness (current) levels for tail lamp and stop lamp illumination can be set separately. Finally, the new product provides failsafe functionality in the form of a P-BUS and LED open/short protection functions.

ROHM, which offers a broad range of LED driver products for use in mobile phones, thin-panel displays, and other devices, has earned praise from customers in the LED driver LSI market thanks to features such as low current consumption, high reliability, and high precision. The development of the BD8372HFP-M was made possible by the exhaustive range of capabilities ROHM brings to the table, including extensive expertise in LED driver circuit technology and a commitment to delivering high levels of quality and reliability, for example by building a dedicated production line for the automotive market. Going forward, the company plans to further strengthen its portfolio of LED driver LSI products for the automotive electrical component market, which is expected to continue to experience dynamic growth.

■Principal features of the BD8372HFP-M LED driver LSI for automotive tail lamps

High-precision output current of ±3%

Support for separate high/low current settings

Built-in LED open and short protection

Built-in P-BUS function

■Comparison of LED Current Precision (for a 3-LED connection)

■Terminology

Source driver design A design in which the current that drives the LEDs is supplied from the LSI as the source. Since the LSI and LEDs share an anode connection, with the LED's cathode connected to ground, the design requires only a single connection between the control board and LED board.

P-BUS function A function that allows the design of systems in which all LEDs turn off when a single LED lamp changes to open when driving LEDs using multiple drivers with a P-BUS (Protect Bus).

LED open/short protection function A function that detects an open (broken wire) or short (grounded wire) state in an LED connected to the driver and outputs an error flag.